Reviews of Environmental Education Materials:Biology, 4th ed. by Peter Raven and George Johnson

review by Wm. Robert Johnston
last updated 24 May 2002

The text makes a number of factual errors in its presentation and in application of the scientific method. This listing of errors includes only those pertaining to environmental concepts.

The authors make many claims concerning environmental issues which are variously unsupported scientifically, ethical in nature, or just plain wrong. Much of chapter 28 is flawed in this regard; contrast the crisis tone of this chapter to the rest of the book (a prime example being p. 619, "On the first day of November 1986, the Rhine almost died.").

The text claims in several locations (pp. 533, 539, 611) that the world's population is surpassing or nearly surpassing its carrying capacity. The world can in fact support several times as large a population as the United Nations' worse case equilibrium projections, even assuming no change in technology. The facts flatly contradict the claim on p. 615, "We clearly already have more people than can be supported with current technologies." When problems in the third world are cited as evidence for surpassing of carrying capacity, this shows a lack of scientific control for poverty and access to resources. The authors support their claims twice with the statement "humans are consuming, wasting, or diverting an estimated 40% of the total...photosynthetic productivity on land" (pp. 611, 613).

Page 618 claims that depletion of fossil fuels has prompted the search for alternative fuels. This depletion is perceived and not real; the world is farther from exhausting known reserves now than in 1980. Costs of fossil fuels indexed to wages have been declining consistently for the past generation. The same page falsely claims that nuclear power is "not cheap", when in fact it is less expensive than oil, coal, and contemporary solar power.

Regarding global warming, the authors begin on p. 619 with a physically incorrect definition of the greenhouse effect. It misrepresents the contribution of every greenhouse gas other than carbon dioxide. The text claims that if the polar ice caps melt that "sea levels would rise by more than 150 meters." In fact, melting all polar and glacial ice on the planet would raise sea level by only 75-80 meters, and would take probably thousands of years.

The authors draw several unscientific connections concerning ozone depletion. They start with the term "ozone hole" which perpetuates student misconceptions of the phenomena. Available evidence does not permit the cited conclusions that depletion began in 1975, that it is consistently worsening, that CFCs are the principal cause, and that depletion will inevitably continue. They cite false statistics on depletion rates on p. 624 (3%), and then erroneously infer a connection to skin cancer rates. The conclusion "Skin cancers are one of the more lethal diseases afflicting humans" is false, even if discussion is limited to cancers: skin cancers are among the most treatable cancers, and the form which is most lethal (melanoma) is biologically unrelated to ozone depletion.

The statistics on tropical deforestation on p. 625 are wrong: existing tropical forests are three times more extensive than claimed and deforestation rates are less than half of claimed rates. The claim "there will be little undisturbed tropical forest left anywhere in the world by early in the next century" is not scientifically founded.

Extreme assertions are made concerning species extinction and loss of biodiversity, but these claims rest on dubious extrapolations and are short on scientific verification. The cited claims on p. 599 and p. 627 of 20-25% of species extinct in the next 30 years represent the fringe of the scientific community, must make a multitude of untestable assumptions in applying the species-area relationship, and are simply not borne out by observation. From 1600 to 1994 only 977 species of animals and vascular plants were documented as becoming extinct; this includes less than 100 species of animals in the 20th century extinct due to habitat destruction.

In more than one instance the authors apply their unscientific conclusions to calls for politics.

Additional items:

p. 210: the solar energy reaching the earth "each day is the equivalent of about 1 million Hiroshima-sized atomic bombs"

Actual ratio is 270 million.

p. 409, Figure 18.10: "incidence of cancer...is centered in cities and in the Mississippi Delta. This distribution suggests that pollution and pesticide runoff may contribute to the development of cancer."

Correlation does not prove causality. Even only addressing the correlation, the mapped distribution is poor support of the hypothesis: Los Angeles is one of the most polluted cities (in terms of air pollution) but does not have a high cancer rate. Cancer rates in southern cities are high partly due to migration of senior citizens from the north. The highest cancer rates in Louisiana are not areas directly receiving Mississippi River runoff, arguing against the pesticide hypothesis. High cancer occurs in scattered rural counties as often as urban areas.

p. 409, Figure 18.10(c)

Number of manufactured cigarettes is not equivalent to that of consumed cigarettes, due to import and export.

p. 417, "The price of smoking this pack of cigarettes is 3 1/2 hours of your life."

While the point is well taken, care should be taken not to give a false impression concerning risk assessment. Students need to understand that the nature of risk is random.

p. 418, "Cigarette manufacturers have argued that the causal connection between smoking and cancer has not been proved, and that somehow the relationship is coincidental. Look carefully at the data presented in figure 18.D and see if you agree."

Figure 18.D graphs average cigarette consumption and cancer incidence by sex vs. time. This is the wrong graph to use to draw a scientific connection between smoking and cancer because it does not control for other variables which have changed over time. The authors should have presented graphs of cancer rates vs. individual smoking habits.

Ehrlich has established himself as making very unscientific claims concerning the population explosion, and in doing so has called for policy changes arguably detrimental to the human condition.

p. 533: "The human population is climbing rapidly and has now attained the unprecedented level of nearly 6 billion people... This severely strains the earth's capacity to sustain us all."

p. 539: "...both the current human population level and the projected rate of growth have potential consequences for our future that are extremely grave."

p. 611: "population...could range from 8.5 billion to nearly 20 billion, and the difference is of key significance for the quality of life on earth."

Human carrying capacity for the earth, given the resource needs of our current level of technology, is one or two orders of magnitude greater than this. Current problems which have been attributed to a large human population are a reflection of political restrictions on resource distribution and not of resource depletion. For a number of reasons the analogy of ecological carrying capacity does not apply to the current human situation.

p. 586: "...the depletion of the ozone layer, apparently as a result of human activities, poses serious ecological problems."

It is not clear, scientifically or otherwise, whether the ozone layer is being depleted or if we are observing natural cycles, or that the depletion is the result of human activity.

p. 599: "The disturbance and destruction of tropical rain forests will be accompanied by the extinction of as many as a quarter of the total species on earth during the next 50 years."

This figure is not supported by actual evidence.

p. 618: "Thirty-one individuals died as a direct result of radiation poisoning" in the Chernobyl accident.

In fact, the first two deaths resulted from mechanical and thermal injuries from the explosion itself; 29 others died of radiation sickness which is sometimes distinguished biologically from radiation poisoning.

p. 697: "...elimination of malaria worldwide...this hope was soom rendered impossible by the development of DDT-resistant strains of malaria-carrying mosquitoes... [DDT's] effectiveness in controlling mosquitoes is dropping."

The international restrictions on use of DDT, originating with the U.S. EPA and now coming into effect in remaining third world countries, is a greater factor in resurgence of malaria. This is demonstrated by the immediate increase in malaria in many countries when DDT was abruptly banned.